Design and fabrication of low cost thick film pH sensor using silver chlorinated reference electrodes with integrated temperature sensor

Abstract

This paper describes the design and fabrication of thick film pH sensor, in which the reference electrode has been formed by chlorination of Ag using FeCl3. The process was aimed to replace Ag/AgCl paste commonly used as reference electrodes. Fabricated using thick film screen printing technology on Al2O3 substrate, the pH sensor showed a measured sensitivity of -52.97, -53.17 and -53.68 mV/pH at 25°C, 45°C, and 65°C, respectively. The measured values were close to the theoretical Nernstian slope of -59 mV/pH 25°C. The sensor was also designed with an integrated Ruthenium based temperature sensor for future temperature compensation. The measured resistance temperature characteristics showed a linear reasponse over the range of 25 - 80°C. This miniaturised planar sensor should find wide application, especially in field water quality monitoring, replacing their glass type counterparts.